Nature Blog Network

Sunday, March 24, 2013

4. Trees and Wildflowers in the Piedmont Mesic Forest: Early Spring


One of the best places to see and learn about the diversity of plants in the piedmont of Georgia is the Southern Piedmont Mesic Forest, an ecological community unique to the piedmont of the southeastern U.S.  It  is a great place to go to with your tree and wildflower identification guides and learn about the natural plants of Georgia, especially in the Spring when wildflowers are in bloom.

The Piedmont
The piedmont is the region of rolling hills in north-central Georgia that lays south of the Appalachian Mountains and north of the flat Coastal Plain.  The majority of the people who live in Georgia live in the piedmont region since Atlanta and other piedmont cities have large populations.

The Georgia Piedmont is represented by the area in green.  Photo Credit: Wikimedia Commons/Public Domain.
Piedmont Oak-Pine Forests 
Before talking about the mesic forest of the piedmont, I want to mention the more typical forest type of the piedmont, so that you'll understand why the mesic forest is different.  The natural plant community on the upper slopes and tops of the hills in the Georgia Piedmont is the Oak-Pine Forest, also known as the Oak-Hickory-Pine Forest.  These upper slopes of the piedmont hills typically have drier soils, known as xeric (pronounced zeer-ik) soils, since rainfall runs downhill away from these areas and they subsequently dry out quickly.  Due to the geology of the piedmont, the soil also typically has an acidic pH.  The dry, acidic soil conditions limit the species of trees and other plants that can grow on these upland sites.  This is because the acidic pH makes it harder for plants to absorb nutrients from the soil, and many trees and other plants need more moisture than is available in this type of environment.

Typical Piedmont Oak-Pine Forest in March.

The leaf litter in an Oak-Pine Forest is a mixture of deciduous leaves and pine needles.  In areas with a high concentration of pines the pine needle leaf litter can lower the soil pH and make the soil more acidic.
For more detailed information about this ecological community, see the Natureserve Explorer Ecological System Comprehensive Report.  Go to: http://www.natureserve.org/explorer/servlet/NatureServe?init=Ecol and enter "Southern Piedmont Dry Oak Pine Forest" in the ecological unit field and press enter.

Piedmont Mesic Forests
There are some areas on the northern and lower slopes of some piedmont hills where much richer natural plant communities grow, some of the most species-diverse in the piedmont.  These areas are moister, or more mesic (pronounced mez-ik), and are known as Mesic Forests.  The higher moisture levels support more species of trees and other plants than the  xeric Oak-Pine Forest.  The mesic conditions exist because these areas are either at the bottom of slopes where rainwater drains into the soil, or they are on the north-facing sides of hills.  The north sides of hills don't get any direct sunlight, even in midsummer, since the sun is always a little to the south of our latitude even at high noon.  As a result the sun does not dry out the soil as it does on the East, South, and West slopes of hills.  These mesic soils are not water-logged or wet; they are typically well-drained but have higher moisture levels.  These plant communities should also not be confused with alluvial floodplains (found along rivers) or riparian forests (moist areas along streams and creeks).  The mesic forest is distinguishable because it is upslope from these other natural communities.

You'll be able to identify a Mesic Forest because beech trees (Fagus grandifolia), which require mesic conditions, are either the dominant tree species or are very abundant.  Other tree species that prefer or require mesic conditions will also be present, including species like musclewood (Carpinus caroliniana) and tuliptree (Liriodendron tulipifera), and will help you to confirm that you have found a mesic site. Most piedmont mesic forests have an acidic pH level less than 7.0, but they still support a diverse plant community. 

To see images and descriptions of any of the trees in this post go to the Virginia Tech Forest Biology and Dendrology site and search for the tree species:  http://dendro.cnre.vt.edu/dendrology/factsheets.cfm

For more in-depth information on each tree species in this post, go to the U.S. Forest Service's Sylvics of North America, Volume 2, Hardwoods:
http://www.na.fs.fed.us/pubs/silvics_manual/volume_2/vol2_Table_of_contents.htm

A Piedmont Mesic community is recognizable by the abundance of Beech trees (Fagus grandifolia).  This photo shows a north-facing mesic slope in March.  Click on the photo to get a larger image so that you can see the smooth gray trunks and distinctive buttressed roots of the large beeches on the hillside.  They are distinctive whether it is winter or summer.  The smaller beech saplings have persistent leaves that stay on the trees throughout the winter, making them easily recognizable in the winter forest.  They are visible in this photo as the small trees with light brown leaves.
For more detailed information about this ecological community, see the Natureserve Explorer Ecological System Comprehensive Report.  Go to: http://www.natureserve.org/explorer/servlet/NatureServe?init=Ecol and enter "Southern Piedmont Mesic Forest" in the ecological unit field and press enter.

Piedmont Basic Mesic Forests
These mesic forests are rarer, but have conditions that support even more plant diversity and are an exciting place to see and learn about plants.  This is because they have minerals in the underlying rocks, usually calcium or magnesium, that buffer the soil pH and make it less acidic.  These forests are sometimes referred to as Basic Mesic Forests.  Basic refers to a pH level greater than 7, which is typically not found in these forests, but the name indicates that they include minerals with a basic pH such as calcium and magnesium. Basic mesic forests typically have a well-developed understory and many different species of herbaceous plants.  Many of these plant species are not found elsewhere on the piedmont but instead are normally found in the mountains.  Exploring a basic mesic forest during Spring or Summer will provide you with a wonderful opportunity to view a wide variety of trees, herbaceous plants, and wildflowers.

A Trip Through a Basic Mesic Forest in Mid-March, 2013
Mid-march in Georgia's northern piedmont is when the very first Spring wildflowers begin to emerge and bloom in mesic forests.  Our first field trip into the forest after the winter was to a Basic Mesic Forest.

The Basic Mesic slope we explored in March.  The slope faces north and has beech trees.  The underlying rock strata cause rainwater to flow into this part of the slope, where it trickles out and forms the beginning of a small branch (brook). 


Another view of the same area with me standing upslope.  The hillside is steep and at least 70 feet high.  The old 55 gallon metal drum at the bottom may be from an old still.  We have found the remains of many early twentieth-century stills throughout the forests of north Georgia.   Moonshine, or White Lightning, was produced illegally in small stills by individuals across north Georgia.  We typically find the still sites upstream near the beginnings of small brooks in forests. 





This is the same photo that was used above to show Beech trees.  It is part of the Basic Mesic slope and shows the large Beech trees that are abundant on the slope.

Another tree on the slope, Musclewood (Carpinus caroliniana).  Like Beech, it also grows along creeks and rivers where there are mesic soil conditions.  It is a small to medium size tree with smooth gray bark  and a distinctive rippled, muscled-looking trunk.

This tree, Eastern Hophornbeam (Ostrya virginiana), is also a distinctive small to medium size tree with bark that peels.  If they are common at a site, as on this slope, it can be an indication that the soil is more circumneutral (closer to a neutral pH of 7.0).
There were also several rather large umbrella magnolias (Magnolia tripetala) over thirty feet tall.  The man standing next to the magnolia in this photo is over six feet tall.  Umbrella magnolias also prefer more circumneutral soil.

This site is unusual because there are thousands of Trillium decipiens carpeting the slope and the lowland area below the slope.  This trillium is found in rich mesic sites in a limited range in Florida, Alabama, and Georgia and emerges very early in the Spring. 

A closer look at the T. decipiens.  This amazing display of these unusual woodland plants is one of the reasons we visited this site.  It is an early reminder that Spring is almost here.

Trillium decipiens in bud.  The knife is 4 3/8 inches long.

In bloom on the slope was Hepatica americana, another mesic species and very early blooming wildflower.  The blossom is small, under an inch across.


As you can see, even in the very earliest stage of Spring, a basic mesic forest can be a fun place to visit to see the plant community.  This site will have other species of plants blooming throughout the Spring.

-Wayne

2 comments:

  1. I really enjoyed your posts. I hope you will continue to contribute. I am working on a natural history of the Alpharetta Big Creek Greenway, which has some interesting anthropological components. Let me know if you would be willing to answer occasional questions. Best Regards, Terry Schiff terryschiff99@gmail.com

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